Abstract The Chalk is an unusual karst aquifer with limited cave development, but extensive networks of smaller solutional conduits and fissures enabling rapid groundwater flow. Small-scale karst features (stream sinks, dolines, dissolution pipes, and springs) are common, with hundreds of stream sinks recorded. Tracer velocities from 27 connections between stream sinks and springs have median and mean velocities of 4700 and 4600 m d −1 . Tests to abstraction boreholes also demonstrate very rapid velocities of thousands of metres per day. Natural gradient tests from observation boreholes have rapid velocities of hundreds of metres per day. There is strong geological control on karst with dissolution focused on stratigraphical inception horizons. Surface karst features are concentrated near the Paleogene boundary, or where thin superficial cover occurs, but rapid groundwater flow is also common in other areas. The Chalk has higher storage and contaminant attenuation than classical karst, but recharge, storage and flow are influenced by karst. Point recharge through stream sinks, dolines, losing rivers, vertical solutional fissures, and soakaways enables rapid unsaturated zone flow. Saturated zone networks of solutional fissures and conduits create vulnerability to subsurface activities, and enable long distance transport of point source and diffuse pollutants, which may be derived from outside modelled catchment areas and source protection zones.

ABSTRACT Limestone provides many lessons about Earth’s systems (geosphere, hydrosphere, atmosphere, cryosphere, and biosphere) through the geochemical, hydrologic, ­tectonic, and rock cycles. Limestone is ideal for teaching cross-disciplinary STEM (science, technology, engineering, and math) subjects of biology, chemistry, and physics, along with history and culture through its uses in society as a valuable economic resource. Carbon and calcium chemistry is part of the everyday environment, and limestone deposits around the world are important archives of biotic and abiotic Earth history. Limestones provide data for reconstructing global climate change and provide important “documents” for recreating Earth’s changing biodiversity throughout geologic time, including human history. Limestone precipitation is Earth’s antidote to global warming. Limestone is volumetrically one of our most valuable natural resources with a variety of uses, as well as frequently involved with natural and human-induced environmental hazards. Limestone is a common commodity readily available to all teachers and students, thus it is the ideal material for ­budget-strapped STEM educators to use to address Next Generation Science Standards. Some uses include: using fossils to develop concepts of paleoecology and evolution; using limestones to reconstruct ancient geography (including plate tectonics); and addressing the relevance of limestone to our society as a building stone, for its medical uses, and as a potential hazard associated with karst (caves and sinkholes). Five cross-disciplinary content concepts are addressed to aid teachers in preparing limestone-centric instruction: (1) enhancement of the understanding of chemical reactions and geochemical cycles, (2) biological evolution, (3) physics applications, (4) economic and environmental impacts, and (5) historical and fine arts’ use of limestone.

Abstract The Škocjan Caves are included in UNESCO’s World Heritage List due to their outstanding natural features. The caves include a large underground canyon containing the Reka River, collapse dolines with vegetation in rock fissures and impressive archaeological sites with a rich history of speleological and scientific research. They are also included in the Ramsar Directory of Wetlands of International Importance. Together with their broader surface area, the site is known as the UNESCO Karst Biosphere Reserve. The aim of the management of the reserve is to protect the World Heritage Site and to preserve its outstanding universal value for future generations. The protection activities are regulated by the provisions of international documents, the Škocjan Caves Regional Park Act and the park’s management plan. These activities include monitoring of the water quality in the Reka River and meteorological surveys on the surface. Monitoring of the microclimate of the caves focuses on measuring the effects of tourism and monitoring the levels of radon, with the aim of the ensuring the safety of the park’s employees. Ensuring a favourable status for the underground habitats and species is laid down in the Natura 2000 management programme. Particular attention is paid to ensuring high-quality, safe visits to the caves and providing educational and awareness-raising activities on the surface of the park.

Modern scientific study of karst phenomena came into being during the 90 years before the Geological Society of America was founded in 1888. It began with broad acceptance of the uniformitarian principle (1800s), basic understanding of processes of carbonate and sulfate rock dissolution and precipitation (1820s), and the equations of Hagen, Poiseuille, and Darcy for groundwater flow in porous, fractured, and soluble media (1840–1856). The Dalmation descriptive name “karst” (meaning “stony ground”), adopted by regional surveyors and travelers, came into general use in the 1850s also. The first U.S. Geological Survey (USGS) report on hydrogeology by Chamberlin in 1885 was one of many early texts that stressed the importance of conduit flow in limestone areas. The 50 years following 1888 were dominated by studies in the “classical” karst region of western Slovenia, including definition of the principal types of surface landforms and proposals for their development within cycles of erosion, two sharply contrasted models for storage and flow in limestone aquifers, and promotion of a theory that accessible caves formed chiefly in the vadose zone. Following publication of a USGS report on the major springs in the nation in 1927, American scientists entered the debates in force, proposing that caves should develop primarily below the water table, along it, or create it; they also emphasized the importance of soil CO 2 in boosting rates of solution in carbonate rocks. Russian investigators established the principles of mixing corrosion. The pace of development throughout karst studies accelerated after the Second World War. In the later 1940s and 1950s, the formative studies of solution kinetics began, while improvements in methods of measuring solute concentrations set the stage for global rate models to be developed in succeeding decades. Spatial quantitative analysis came to dominate study of surface landforms, particularly sinkhole distribution patterns. The confusion that had arisen regarding the development of meteoric water (epigene) caves was resolved with a general model emphasizing the controlling roles of lithology and geologic structure: Increasingly, it was recognized that these two variables also explained many of the differences observed between karst aquifers and landform assemblages in different geographical areas. Opening of China to western scholars after 1980 gave access to the astonishing karst lands in the south of that country.

The Nullarbor Plain of southeastern Australia, ∼200,000 km 2 in area, is flat and mostly treeless. It contains widely scattered collapse dolines and a few hundred caves, some of which are large and extensive. Initial karst development probably occurred during the warm, seasonally wet climatic conditions of the Oligocene, when the withdrawal of the sea exposed the recently deposited Eocene Wilson Bluff Limestone for over ∼10 m.y. Several major conduits probably developed at this time. These were flooded by the return of the sea, which finally retreated in the late Miocene followed by regional uplift. Cave formation in the Pliocene and Quaternary was inhibited by the semiarid climate, which became increasingly arid ca. 1 Ma. The overall dryness caused crystallization of evaporite minerals in cracks and pore spaces within the limestone walls of the caves, and they suffered extensive collapse, producing large passages, dome chambers, and dolines. However, during a wet phase 5–3 Ma, rivers extended across the karst plain, and caves formed where they sank into the limestone. Shallower caves probably also formed at this time, perhaps associated with perched water tables. The Nullarbor Plain did not develop extensive surface and underground karst features, even during the wetter climate of the Oligocene. It appears that the flatness of the plain and the particular characteristics of the limestone (primary porosity and lack of jointing and inception horizons) resulted in relatively uniform downwasting and little cave formation. Climate played a relatively minor role in restricting karst development.